The present invention relates to a method and a device for controlling a gas flow over a throttle valve in an internal combustion engine. The present invention concerns, in particular, a method and a device for use in automotive engineering.
An air/fuel mixture is ignited in the combustion chamber of an internal combustion engine to generate an engine torque. The gas mass filling the combustion chamber must be controlled and detected as accurately as possible because it determines, among other things, the engine torque, the fuel volume to be injected, and the ignition point.
Using an xe2x80x9celectronic gas pedalxe2x80x9d in modern engine control systems, the pedal position is interpreted as a torque request. This torque request is converted to a setpoint for the air mass flow. A xe2x80x9ccharge controlxe2x80x9d function calculates a setpoint air mass flow from the torque request and generates from this value a setpoint for controlling the throttle plate. A control element adjusts the throttle plate to the setpoint. A downstream hot-film air mass sensor measures the actual air mass flow. Based on tolerances in the hot-film air mass sensor and in the calculation path of the calculation of air mass flow over the throttle valve, a difference is produced between the actual value and the setpoint of the air mass flow and between the actual torque and the torque request.
To correct these inaccuracies, an adjustment system that has not only one adjustment unit, but two adjustment units, is described in European Patent No. 575710. In a convention device, the first adjustment unit sends the actuating signal to the adjustment path, while the second adjusting unit is used to calibrate the first adjusting unit. In the known device, a throttle-plate-based charge signal is used to control injection, with this relatively fast adjusting signal being calibrated by an air mass meter in the stationary state.
The object of the present invention is to provide a method and a device for controlling a gas flow over a throttle valve in an internal combustion engine, thereby adjusting the gas flow quickly and precisely. In addition, it must be possible to carry out the method as well as produce and operate the device economically.
The object is achieved, in particular, by providing a method for controlling a gas flow over a throttle valve in a combustion chamber of an internal combustion engine having the following steps: calculation of a throttle setpoint setting from the setpoint gas flow, activation of the throttle valve using the throttle setpoint setting, and determination of an actual gas flow, characterized by the following steps: calculation of a gas flow over the throttle valve on the basis of an actual throttle setting, determination of a difference between the calculated gas flow over the throttle valve and the actual gas flow, and taking into account the determined difference when calculating the throttle setpoint setting, in particular by adjusting the setpoint gas flow. In doing this, the setpoint air mass in the combustion chamber is advantageously converted in one step to a throttle valve setpoint at which an actual air mass begins to form with the accuracy of the sensor used to determine the actual gas flow. A hot-film air mass sensor can be used, in particular, as the sensor for determining the actual gas flow. A further advantage lies in the fact that, unlike the related art, an additional charge controller, which subsequently adjusts the setpoint and actual mass, is not used. This reduces the production, maintenance, and operating costs. A further advantage lies in the fact that the single-step control stabilizes the throttle plate characteristic, thereby improving the operation of the entire internal combustion engine unit. A further advantage lies in the fact that the method makes it possible to adjust the desired air mass flow very quickly and precisely. In the steady state, in particular, there is no difference between the setpoint charge and the actual charge measured by the hot-film air mass sensor.
In one particular embodiment of the present invention, the method is characterized by a determination of at least two correction quantities when taking into account the difference between the gas flow over the throttle plate of the throttle valve and the actual gas flow. This has the advantage that the determination of at least two correction quantities makes it possible to achieve faster and more precise control. An additional advantage lies in the fact that the determination of at least two correction quantities provides for the separate treatment of and compensation for different error quantities and disturbances, thus further improving control accuracy and speed.
In a further embodiment of the present invention, the method is characterized by additively taking into account at least one first correction quantity and multiplicatively taking into account at least one second correction quantity, with the first and second correction quantities being taken into account simultaneously or alternately, in particular the first correction quantity being taken into account, i.e., being relevant, primarily in the case of small gas flows and the second correction quantity being taken into account, i.e., being relevant, primarily in the case of large gas flows over the throttle valve. In a further embodiment of this design, the first correction quantity corrects an error caused by leakage air over the throttle valve, and the second correction quantity corrects an error caused by an incorrect detection of a pressure upstream from the throttle valve. This is advantageous because it allows the two errors to be handled according to their specific error characteristics, thus increasing control accuracy. One advantage lies in the fact that an error caused by leakage air, which is made noticeable by an additive error in any operating state, but is not relevant especially with small gas flows, can be treated accordingly. Likewise, an error caused by erroneous pressure detection, which is noticeable in any operating state and is relevant, in particular, with large gas flows, can also be treated accordingly. The two correction quantities can be preferably taken into account simultaneously, thus achieving a high control accuracy. Overall, an embodiment of this type provides very fast and yet highly accurate and reliable control, at the same time lowering costs of both equipment and computer-supported control.
In a further embodiment of the present invention, at least one of the correction quantities is stored at the end of operation of the internal combustion engine. This advantageously provides full control accuracy as soon as the internal combustion engine resumes operation. The correction quantities can be advantageously stored by appropriate electronic components, for example by an SRAM component or a magnetic storage device.
In a further embodiment of the present invention, a predetermined value is used as a starting value for at least one of the correction values when operation of the internal combustion engine resumes. This is advantageous because it allows a selected cold-start value to be easily determined for specific correction quantities. The provision of predetermined values is also advantageous because it maintains secure control even if the internal combustion engine is idle for an extended period of time or if data or information relating to the predetermined correction quantities is lost.
In a further embodiment of the present invention, the setpoint gas flow is determined on the basis of at least one request for the torque of the internal combustion engine. This is advantageous because, in a motor vehicle with an internal combustion engine, not only can the torque request via the gas pedal be taken into account, but also torque requests that are produced by an automatic transmission of the motor vehicle or by an anti-spin control system of the motor vehicle.
The object of the present invention is also achieved by providing a device for controlling a gas flow over a throttle valve in a combustion chamber of an internal combustion engine including a throttle valve controller having an input signal for a setpoint gas flow and an output signal for a valve position, and a measuring sensor for determining an actual gas flow, characterized in that the throttle valve controller has a computing device which calculate a gas flow over the throttle valve on the basis of the throttle setting, and which further determines a difference between the calculated gas flow over the throttle valve and the actual gas flow, with this difference being taken into account when calculating the output signal, in particular by adjusting the setpoint gas flow. A device of this type according to the present invention has the same advantages mentioned above in connection with the method according to the present invention. In particular, a device of this type is advantageous because it ensures fast and precise control, at the same time reducing the apparatus and computing requirements so that a device of this type can be produced, maintained, and operated economically.
In one embodiment of the present invention, at least two correction quantities are determined when determining the difference. This has the advantage that even complex error quantities and disturbances can be detected quickly and with relatively little effort, achieving stable and precise control. This is particularly true when the at least two correction quantities separately detect error sources with additive and multiplicative error characteristics and preferably take them into account simultaneously.
The subject matter of the present invention also includes a device that carries out one of the above-mentioned control methods according to the present invention. This combines the advantages of fast and accurate control with an economical implementation by a device according to the present invention.
The subject matter of the present invention also concerns a motor vehicle that has a device like the one described above.
The present invention also relates to data media which contain a control program for carrying out one of the above-mentioned control methods according to the present invention, or which contain the parameters that are necessary or advantageous for carrying out one of the above-mentioned methods according to the present invention. The data media can store the information in any form, in particular in mechanical, magnetic, optical or electronic form. In particular, electronic data media are advantageous, for example a ROM, PROM, EPROM or EEPROM device that can be advantageously inserted into corresponding control units. Data media of this type can be used to easily exchange control parameters and control programs, thus making it possible, for example, to configure a standard control unit for different vehicle types simply by inserting the corresponding data medium.